1. FIELD OF THE INVENTION
This invention pertains to a process and apparatus for separating a mixture of immiscible liquids containing particulate carbon. More specifically, it relates to a decanter for separating a liquid-mixture comprising particulate carbon as produced by the partial oxidation of a hydrocarbonaceous fuel, water, and liquid organic extractant into a stream of particulate carbon dispersed in said liquid organic extractant and a stream of clarified water.
2. DESCRIPTION OF THE PRIOR ART
The partial oxidation of liquid hydrocarbons, especially heavy fuel oils, represents a highly economical method for the production of synthesis gas in large quantities. The effluent gas stream from the gas generator comprises H.sub.2, CO, H.sub.2 O, CO.sub.2 and at least one gas from the group H.sub.2 S, COS, N.sub.2, Ar, and CH.sub.4. Further, about 0.2 to 20 weight percent (basis C in the feedstock) of particulate carbon i.e. soot may be entrained in the stream of gases leaving the gas generator. It may be necessary in certain applications to remove the particulate carbon from the process gas stream. For example, to extend the life of catalysts that may be used in down-stream process steps e.g. water-gas catalytic shift reaction, it is advisable to employ a feed gas which is free from entrained solids.
The solid particulate carbon produced in the partial oxidation process is liberated as very fine particles which are easily wet by water or oil. In coassigned U.S. Pat. No. 2,992,906--F. E. Guptill, Jr. the particulate carbon entrained in the process gases issuing from the gas generator is removed by scrubbing with water in a conventional gas-liquid contact apparatus, for example spray towers, and bubble or packed towers. A large volume of carbon-water dispersion is produced in the scrubbing zone containing less than about 2 percent solids, and preferably about 1 percent solids for satisfactory pumpability.
Economics and the avoidance of water pollution require that the carbon be separated from the water and recycled to the gas generator as a portion of the feed. The clarified water may be then recycled to the scrubbing zone. This separation may be accomplished by intimately contacting the carbon-water dispersion with a liquid hydrocarbon. The mixed stream is then passed into a separating zone where clarified water may be separated from a slurry of particulate carbon and liquid hydrocarbon.
In previous separators the feed was introduced at one end and the effluent stream was removed from the opposite end. Standing waves were produced in the vessel along with emulsions that interfered with the separation between the water and the dispersion of carbon and liquid hydrocarbon. Further, only about half of the volume of the vessel was used. These difficulties have been avoided by the subject invention.